Processes and apparatus for embossing precision optical patterns, such as microcubes, or prisms, in a thin film resinous sheet or laminate, are known as referenced in U.S. Pat. Nos. 4,486,363; 4,478,769; 4,601,861; 5,213,872; 6,015,214, and more recently 6,908,295, the subject matter of which patents are all fully incorporated herein by reference. In the production of such synthetic resin optical sheeting film, highly precise embossing (generally exceeding the capabilities of current micromolding processing techniques for synthetic resins), is required because the geometric accuracy of the optical prismatic elements determines the film's optical performance. The above referenced patents disclose particular methods and apparatus for continuously embossing a repeating retro-reflective microprismatic pattern of fine or precise optical quality and detail on one surface of a transparent and thin thermoplastic film to form the surface of the film into the desired retroreflective microstructured pattern.
This application relates to significant improvements to the method and apparatus of prior patent, U.S. Pat. No. 4,618,518, issued Jun. 21, 1986, of which the current inventor is a named co-inventor thereof. This prior patent is incorporated herein by reference.
To manufacture current traffic signs, the thin retroreflective microprismatic pattern in thermoplastic film is then combined with a protective backing layer behind the microprismatic elements, and then there is applied an additional pressure sensitive adhesive and a release liner. Subsequently the release liner is removed and the adhesively backed film is then applied to an underlying aluminum or other material substrate. This combination of materials is known as reflective sheeting, in which the film is produced in rolls in various specified colors and then laminated to the aluminum or other material panels to produce the primary components for traffic signs. Lettering and symbols can be printed or laminated as film on the front film surface to provide text or other instructions to a driver. Prior to corner cube prisms, products such as those consisting of glass bead film, known as engineer grade, and high-intensity films have been used for decades. More recently the improved versions use micro prismatic optics formed on the reflective film, which is more efficient and capable of a diverse range of reflectivity that is beneficial to the driver at night. Nonetheless, the retroreflective sheeting products currently produced, as manufactured by numerous companies, are produced with the backing layer, the adhesive layer and the release liner and then shipped to sign shops that fabricate the signs where the film is then laminated to aluminum or other material panels using the pressure sensitive adhesive. This technique currently now is, and has been universally used for decades as the primary method of manufacturing retroreflective traffic signs. There are several companies that manufacture the retroreflective sheeting film and many companies that provide the aluminum panels. Sign makers purchase the reflective sheeting with the back layer, adhesive layer and release liner from one source and the aluminum panels are purchased from another source and then the sign shops combine the two components.